<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script> 
    // let age = prompt('输入年龄')    
    // document.write('我今年'+age+'岁了')
    let num = 12 
    // let sum 
    let tip = false
    let umname = '刘德华'
    let obj = null
    console.log(typeof (sbj))

    // document.write(`我今年${age}岁了`)
    // 模板字符串
    console.log(typeof 'age')
        console.log(typeof (age))
    console.log(typeof (sum))
    console.log(typeof (tip))
    console.log(typeof (uname))
    console.log(typeof (obj))

    </script>
</body>
</html>